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The European magic number: 41

As the size of Monday’s Conservative rebellion over a referendum on EU membership appears to grow – Newsnight on Friday were talking about 100 Conservative MPs defying the whip – David Cameron might well be wishing that he had led the Conservative Party in the 1950s. There were two sessions during that decade in which not a single government MP rebelled. Alternatively, he would no doubt happily swap places with Harold Macmillan, who faced just one Conservative rebel – in the shape of Anthony Fell – when in August 1961 the Commons debated Macmillan’s decision to open negotiations with Europe about possible EEC entry.

It was Edward Heath who faced the first bout of Tory discontent over Europe, following his decision to take Britain into the Common Market. In one remarkable session, 1971-72, Heath experienced no fewer than 88 separate rebellions on the European Communities Bill. The only saving grace was that this came from a hard core of determined opponents. The largest rebellion, in April 1972, saw 18 Conservative MPs support a move to hold an advisory referendum on EU entry. We safely predict rather more than 18 Conservative rebels on Monday.

Margaret Thatcher got away relatively lightly over this issue. In all three of her terms in office combined, over a total of 11 years, she faced fewer rebellions over Europe than Heath had in just four years (and fewer than Major was to face in his seven years). The passage of the Single European Act, one of the largest shifts of sovereignty from the UK, provoked just 11 rebellions, the largest involving ten MPs. Mrs Thatcher’s largest European rebellion of all came over the EC (Finance) Bill in June 1985, when 19 Conservative MPs voted against the whip. Again, we safely predict more than 19 Conservative rebels on Monday.

It was John Major who faced the second, and most serious, bout of Tory discontent over Europe. Hamstrung by a Commons majority of just 21 after 1992, he faced no fewer than 62 rebellions over just one Bill: the European Communities (Amendment) Bill, more commonly known as the Maastricht Bill. These rebellions involved 50 MPs, who between them cast more than 1,100 dissenting votes. Although Heath had experienced more rebellions over Europe in the 1970s, the average Europe rebellion under his leadership had involved fewer than 10 MPs; during Maastricht and Major’s leadership it involved over 18 MPs. There were a further 14 Conservative rebellions on other European issues during the 1992 Parliament. John Major also holds the record (until Monday anyway) of suffering the largest Conservative Government backbench rebellion on Europe on whipped business: on 20 May 1993 some 41 Conservative MPs voted against the Third Reading of the Maastricht Bill.

That same number, 41, is coincidentally also the largest Conservative rebellion so far in this Parliament. On 10 October 2011, 41 Conservative MPs (plus two Lib Dems) supported an amendment to the programme motion for the Protection of Freedoms Bill which would have allowed time on a vote to remove all offences based on insulting words or behaviour.

More than a decade of studying rebellions has made us cautious about claims made about the size of any upcoming rebellions. It is an almost inviolable law that the number eventually discovered to have voted against their whip will be smaller than the figures bandied about in the run-up to the vote. But by Friday, if you combined the list of those Conservative MPs who had signed the referendum with those who have already defied their whips over Europe since May 2010, you got a figure of 78. All the signs therefore are that Monday will produce the largest Commons rebellion of Cameron’s premiership – and the largest ever rebellion by Conservative MPs when in government over the issue of Europe.